1. Field of the Invention
This invention relates to obtaining fructose in high yields with a high degree of purity.
2. Description of the Art Practices
Fructose may be viewed as one-half of a sucrose molecule with the other half being dextrose (glucose). Sucrose is, of course, known commonly as table sugar and is widely used as a sweetener and structurant in many products from cake mixes to soft drinks. It has been determined that the fructose portion of the sucrose molecule has greater sweetening power on an equal weight basis than sucrose or dextrose. Therefore, if fructose is substituted into formulations, the overall cost may be lowered when compared to using sucrose. The use of fructose provides a higher degree of sweetening at a given weight level than sucrose. Thus, fewer calories are present in a fructose-sweetened product at equal sweetening levels than when sucrose is used.
Several routes have been utilized to isolate and separate fructose as a crystalline component. For the most part, fructose is prepared by isomerizing dextrose which is obtained through the refining of corn syrup. The isomerization of dextrose is generally not a 100% conversion and therefore the fructose must be separated from the remaining saccharides, e.g. dextrose, and crystallized from the aqueous dispersion.
The separation of fructose from the syrup is complicated by the high degree of solubility of the fructose in water. Therefore, the separation of fructose at acceptable purity and yield from an aqueous syrup is yet to be accomplished in a practical manner.
U.S. Pat. No. 3,607,392, issued Sept. 21, 1971, to Lauer, describes a process and apparatus for obtaining crystalline fructose through the use of methanol. Methanol has limits on its usage in food products which is the major market for crystalline fructose in the first instance.
U.S. Pat. No. 3,883,365, issued to Forsberg et al on May 13, 1975, describes a separation of fructose from glucose within a narrowly constrained pH range by lowering the temperature of the reaction mixture. The disadvantage in this process is that it is not economical to refrigerate a syrup in a plant setting. That is, the syrup will be at least at an ambient temperature during processing and the mechanics of cooling require the substantial expenditure of energy.
Yamauchi U.S. Pat. No. 3,928,062, issued Dec. 23, 1975, discloses recovering fructose by seeding anhydrous fructose crystals into a supersaturated solution of fructose. U.S. Pat. No. 4,371,402, issued Feb. 1, 1983, to Kubota, describes the dehydration of fructose utilizing an organic solvent having azeotropic behavior with respect to water.
The teachings of Dwivedi et al in U.S. Pat. No. 4,199,373, issued Apr. 22, 1980, relate to anhydrous free-flowing crystalline fructose obtained by allowing a seeded syrup to stand at low temperature and high relative humidity. U.S. Pat. No. 4,199,374, issued Apr. 22, 1980 also to Dwivedi et al suggests seeding a syrup containing fructose and allowing it to stand followed by recovery of the fructose. U.S. Pat. No. 3,513,023 to Kush, issued May 19, 1970, discloses the recovery of crystalline fructose over a broad pH range, through concentration and cooling, following seeding of the mixture.
It therefore remains to effectively separate fructose from an aqueous syrup in a high degree of purity and with a high yield. The present invention, as later described, deals with this problem effectively by using a mixture of two alcohols to separate the components to a superior degree than when using a single alcohol.
Throughout the specification and claims, percentages and ratios are by weight, temperatures are degrees Celsius, and pressures are in atmospheres over ambient unless otherwise indicated. To the extent that any of the foregoing references are applicable to the present invention, they are herein incorporated by reference.